/Engine/Source/Editor/UnrealEd/Classes/MaterialGraph/MaterialGraph.h
Add a Comment to the Graph
UMaterialGraphNode_Comment* Newly created Graph node to represent comment
[UMaterialGraphNode_Comment](API\Editor\UnrealEd\MaterialGraph\UMaterialGraphNode_Comment) * AddComment ( [UMaterialExpressionComment](API\Runtime\Engine\Materials\UMaterialExpressionComment) * Comment, bool bIsUserInvoked )